Breastfeeding is the optimal nutrition for infants and is recommended for the first year of life by the American Academy of Pediatrics. However, mothers who return to work within this time period cannot always breastfeed on demand and often pump their milk and send it with the baby to a day care setting. Infants in the neonatal intensive care unit rely heavily on donor breast milk or their mothersâ€™ own breast milk, all of which is expressed, stored, transported to the hospital, and stored again. There are few guidelines on the length of time that this milk can be kept and the optimum and tolerable storage temperatures for human milk. Guidelines that are sometimes used are based on very few scientific studies of the impact of storage on milk quality and stability. There is a need for science-based standard protocols for milk handling and storage in hospitals and milk banks as well as a need for evidence-based recommendations for safely handling milk at home and in child care facilities.
The objective of the first study was to investigate the effects of storage temperature and time on components in freshly expressed, human breast milk. Eleven breast milk samples were collected from twelve women who volunteered with informed consent. The samples were stored either at -20Â°C, 4Â°C, or 24Â°C. All samples were stored for three weeks and analyzed for total protein and free amino ends, total fat and non-esterified fatty acids (NEFA), bacterial growth, secretory immunoglobulin A (SIgA) activity, and lysozyme activity. Samples stored at -20Â°C only showed a significant increase in NEFA (p < 0.0001). Samples stored at 4Â°C showed a significant increase in NEFA (p < 0.0001), free amino ends (p < 0.0001), and bacterial growth (p < 0.01). Samples stored at 24Â°C showed a significant increase in NEFA (p < 0.0001), free amino ends (p < 0.0001), bacterial growth (p < 0.0001), and a decrease in total protein concentration (p < 0.0001). All samples showed a rapid increase in NEFA (p < 0.0001). Total fat, lysozyme, and SIgA remained stable throughout the storage conditions.
The objective of the second study was to observe the difference in bacterial growth in breast milk contaminated by an infant in motherâ€™s own milk and donor milk and determine if it is safe for infants to drink breast milk from a bottle, store it for a period of time, and then drink from it again. Five women volunteered with informed consent and provided parental consent for their infant to participate. Each infant was fed 1 â€“ 2 ounces of breast milk from a bottle prepared with the motherâ€™s pasteurized milk and the motherâ€™s unpasteurized milk. At least one ounce of leftover milk was collected in sterile containers and analyzed for bacterial growth at specific time points during storage. Leftover samples were stored at 4Â°C for 0 hours, 2, 4, and 6 days, and at 24Â°C for 0, 3, 6, 9, and 24 hours.
Based on the data, it appears that unpasteurized breast milk can be stored up to 6 â€“ 9 hours and pasteurized breast milk between 9 â€“ 24 hours at 24Â°C. Unpasteurized breast milk can be stored between 4 â€“ 6 days and pasteurized breast milk can be stored longer than 6 days at 4Â°C.
Results of both studies indicate that breast milk may be stored longer than suggested by the current recommendations. Understanding safety and quality of expressed, stored, breast milk will allow mothers to confidently extend breast feeding duration when the infant is left in a child care setting or when the infant is in a neonatal intensive care unit.